Myotomes

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A myotome is the group of muscles that a single spinal nerve innervates. Most muscles are innervated by more than one spinal nerve root, and therefore consist of multiple myotomes.

Simplified Examination

Simplified myotome examination based on The Noted Anatomist

Spinal Level	Movement
C5	Shoulder abduction
C6	Elbow flexion
C7	Elbow extension
C8	Finger flexion
T1	Finger abduction
L2	Hip flexion
L3	Hip adduction
L4	Knee extension
L5	Ankle dorsiflexion
S1	Ankle plantarflexion

Commonly Tested Movements

Commonly tested movements. UMN column are movements that are preferentially weak in UMN lesions

Movement	UMN	Root	Reflex	Nerve	Muscle
Upper Limb
Shoulder abduction	++	C5		Axillary	Deltoid
Elbow flexion		C5/6 C6	+ +	Musculocutaneous Radial	Biceps Brachioradialis
Elbow extension	+	C7	+	Radial	Triceps
Radial wrist extension	+	C6		Radial	Extensor carpi radialis longus
Finger extension	+	C7		Posterior interosseous nerve	Extensor digitorum communis
Finger flexion		C8	+	Anterior interosseous nerve Ulnar	Flexor pollicis longus and flexor digitorum profundus (index) Flexor digitorum profundus (ring and little)
Finger abduction	++	T1 T1		Ulnar Median	First dorsal interosseous Abductor pollicis brevis
Lower Limb
Hip flexion	++	L1/2			Iliopsoas
Hip adduction		L2/3	+	Obturator	Adductors
Hip extension		L5/S1		Sciatic	Gluteus Maximus
Knee flexion	+	S1		Sciatic	Hamstrings
Knee extension		L3/4	+	Femoral	Quadriceps
Ankle dorsiflexion	++	L4		Deep peroneal	Tibialis anterior
Ankle eversion		L5/S1		Superficial peroneal	Peronei
Ankle plantarflexion		S1/S2	+	Tibial	Gastrocnemius, soleus
Big toe extension		L5		Deep peroneal	Extensor hallucis longus

Complete Myotome Chart

Complete Myotome Chart

Muscle	Nerve	Spinal Roots
Upper Limb
Trapezius	Spinal accessory nerve	C3, C4
Supraspinatus, infraspinatus	Brachial plexus	C5, C6
Pectoralis major		C5, C6, C7, C8
Latissimus dorsi		C6, C7, C8
Teres major, serratus anterior		C5, C6, C7
Serratus anterior		C5, C6, C7
Rhomboids		C4, C5
Deltoid	Axillary nerve	C5, C6
Biceps and brachialis	Musculocutaneous nerve	C5, C6
Triceps	Radial nerve	C6, C7, C8
Brachioradialis		C5, C6
Wrist extensors (radial)		C6, C7
FCR, pronator teres	Median nerve	C6, C7
FDS, Thenar		C8, T1
FPL, FDP, PQ	Anterior interosseous nerve	C7, C8, T1
EDC, EPL	Posterior interosseous nerve	C7, C8, T1
FCU	Ulnar nerve	C7, C8, T1
FDP radial digits		C8, T1
FDP ulnar digits		C7, C8, T1
Interossei		C7, C8, T1
Lower Limb
Iliopsoas	Femoral nerve	L1, L2, L3
Quadriceps femoris		L2, L3, L4
Adductor longus and magnus	Obturator nerve	L2, L3, L4
Gluteus medius, minimis, tensor fascia lata	Superior gluteal nerve	L4, L5, S1
Gluteus maximus	Inferior gluteal nerve	L5, S1, S2
Semitendinosus, biceps femoris, semimembranosus	Sciatic and tibial nerves	L5, S1, S2
Gastrocnemius and soleus		S1, S2
Tibialis posterior		L4, L5
Flexor digitorum longus		L5, S1, S2
Abductor hallucis, abductor digiti minimi, interossei		S1, S2
Tibialis anterior	Sciatic and common peroneal nerves	L4, L5
Extensor digitorum longus, extensor hallucis longus		L5, S1
Extensor digitorum brevis, peroneus longus, peroneus brevis		L5, S1

Myotome Dance

Myotome Dance

Spinal Levels	Memory Aid	Action
C1, 2	I nod to you	Neck flexion/extension
C3	Don’t tickle me	Neck lateral flexion
C4	I’m not sure	Shoulder elevation
C5	Feel alive	Shoulder flexion, abduction, & lateral rotation
C6, 7, 8	Close the gate	Shoulder extension, adduction & medial rotation
C5, 6	Pick up sticks	Elbow flexion
C7, 8	Lay them straight	Elbow extension
C5, 6	Flick my wrists	Forearm supination
C7, 8	The time is late	Forearm pronation
C6, 7	Fly up to heaven	Wrist flexion & extension
C7	Paper	Finger extension
C8	Rock	Finger flexion (though some sources say C7, 8 does both finger extension and flexion)
T1	Scissors	Finger abduction & adduction
L2, 3	Lift my knee	Hip flexion
L3, 4	Kick the door	Knee extension (& knee-jerk reaction)
L4, 5	Foot points to the sky	Ankle dorsiflexion
L4, 5	Extend my thigh	Hip extension
L5, S1, (S2)	Kick my bum (Run to poo)	Knee flexion
S1, 2	Stand on my shoes	Ankle plantarflexion (& ankle jerk)
L2, 3, 4	Modestly close the door	Hip adduction & internal/medial rotation
L4 - S2	The opposite is true	Hip abduction & external/lateral rotation
C3, 4, 5	Keeps the diaphragm alive	Innervates the diaphragm
S2, 3, 4	Keeps poo off the floor	Innervates bowel, bladder, sex organs, anal sphincter, pelvic muscles. (& anal wink reflex)

Note

• T1-12 Supplies chest wall and abdominal muscles
• L1 Contributes to hip flexion & adduction
• L5, S1, S2 Babinski plantar reflex/extensor response in UMN lesion